In general, shearing systems consist of a shear assembly having an upper and lower frame, and a slide plate. A die assembly with upper and lower shoes is positioned within the shear assembly. Each of the shoes includes a clamp arrangement and blade arrangement. Sheet material such as sheet metal to be cut is placed in a gap between the upper and lower shoes and is positioned with guide apparatus. Hydraulic cylinders are used to drive the slide downward against the upper shoe, depressing it. As the upper shoe is depressed in a downward stroke, first an upper clamp contacts the sheet metal and presses it against a lower clamp. As the upper shoe continues its downward stroke, the sheet is sheared by an upper blade sliding past lower blades.
One problem with conventional shearing systems is that often the sheet is clamped with a bend or a wave in it. This causes the sheet to be sheared while it is not perfectly flat. Accordingly, when the sheet springs back to its pre-clamped state, the sheet has a cut-edge which is not as straight as was intended.
Another problem with conventional shearing systems is that sheet metal may be only partially sheared. In other words, the cut-edge of the sheet may have a rough and pitted area resulting from splitting or breaking rather than from the shearing action of the blades. The rough and pitted area may be difficult to weld to another sheet.
Another problem with conventional shearing systems is that the guide for upward movement of the upper shoe works against the guide for downward movement of the upper shoe. Accordingly, the guides incur increased wear.
It would be desirable to have a shearing system that would clamp the sheet without trapping waves or bends so that a straight cut would be achieved. It would also be desirable to have a blade arrangement that would maximize the actual shearing of the metal sheet with minimal breakage of the cut-edge. It would also be desirable to have a die assembly guide arrangement which would provide a smooth transition between the open and closed position of the die assembly and reduce wear on the guides.